The implantable defibrillator and antiarrhythmic drugs—competitive and complementary treatment for severe ventricular arrhythmia

Abstract

Summary:Most patients with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation (W) are at high risk of recurrence. Implanted defibrillators (ICDs) are highly effective in sensing and converting VT or VF to a perfusing rhythm. "Conventional" antiarrhythmic agents, which primarily block cardiac sodium channels, are relatively ineffective in preventing arrhythmia recurrence; amiodarone and sotalol appear to be effective in reducing recurrence and mortality rates, although the extent of benefit is not well understood. Despite the apparent advantage of ICDs, they have short-and long-term complications, are costly, and their benefit in prolonging the quantity or quality of life remains unproven. Randomized clinical trials which compare the effect of ICDs with that of antiarrhyhuc drugs on mortality, cost, and quality of life will be necessary to understand how patients with malignant arrhythmias ought to be treated. If an ICD is implanted, adjunctive therapies need to be considered to treat the underlying heart disease and to derive optimum benefit from the device. Drugs may have beneficial or adverse interactions with devices, and the full understanding of these interactions requires further study.Key wo& implanted cardioverter defibrillators, antiarrhythmic drugs, ventricular tachycardia The introduction and rapid technologic development of implanted cardioverter-defibrillators OCDs) have caused cardiologists with an interest in rhythm disoders to reevaluate the traditional premise on which antiarrhythmic thempy was basedthat of preventing the Occurrence or recurrence of life threatening ventricular arrhythmm, that is, sustained ventricular tachycardia 0 or ventricular fibrillation 0. It is widely accepted that patients surviving an episode of documented sustained VT, cardiac arrest, or syncope thought to be due to sustained tachyarrhythmia are at high risk of recurrence and of sudden cardiac death, especially in the first year after the initial event. The growing recognition that some antiarrhythrmc agents may not prevent malignant arrhythmias and may indeed increase their likelihood'. 2 has prompted some authorities to suggest that implanted defibrillators should be consided the therapy of choice for patients at risk for sudden death. Additional difficulties with the use of antiarrhythmic drugs include the inability to predict dmg efficacy reliably, even with the use of Holter monitoring or electrophysiologic study, and the risk of adverse effects from drug therapy.Although conceptually inelegant, since the lethal rhythm is not prevented, ICDs are 2 98% effective in diagnosing and converting VT or VF to a perfusiig rhydun (Fig. 1). Should the cardiologic community abandon the search for the "pharmacologic holy grail" in favor of ICDs for all or most patients with VT or VF? A brief review of the evidence in favor and against this approach may place this difficulty in pempective.Antiarrhythmic drug therapy guided by Holter monitoring or electrophysiologic testing (EPS)-although the relati...